Field of the Invention
The present invention relates generally to an electromechanical system for continuously infusing medication into a patient, and more particularly to such a system having a main pump unit onto which is installed a disposable cassette which includes the actual fluid pump used to precisely meter the amount of medication supplied, as well as a battery used as the primary power source for the medication infusion system.
In the past there have been two techniques used to deliver drugs which may not be orally ingested to a patient. The first large dosage at relatively infrequent intervals to the patient. This technique is not always satisfactory, particularly when the drug being administered is potentially lethal or has negative side effects when delivered in a large dosage. This problem results in smaller injections being given at more frequent intervals.
Alternatively, the second technique involves administering a continuous flow of medication to the patient through an IV bottle. Medication may also be delivered through an IV system with an injection being made into a complex maze of IV tubes, hoses, and other paraphernalia. As an alternative to these two techniques of administering medication to a patient, the recent addition of medication infusion pumps has come as a welcome improvement.
Infusion pumps are utilized to administer drugs to a patient in small, metered doses at frequent intervals or, alternatively, in the case of some devices, at a low but essentially continuous rate. Infusion pump therapy may be electronically controlled to deliver precise, metered doses at exactly determined intervals, thereby providing a beneficial gradual infusion of medication to the patient. In this manner, the infusion pump is able to mimic the natural process whereby chemical balances are maintained precisely by operating on a continuous time basis.
Such infusion pumps typically use as a power source a battery, which is contained inside the housing of the device. Most battery-powered infusion pumps use the battery as the power source for the electrical or electronic components used to control the infusion system in addition to using the battery to power the motor or other apparatus used to pump the medication being infused. It may be desirable to include an auxiliary battery such as a small lithium battery to power memory circuits during times when the main battery is being changed, thereby maintaining operating information stored in the solid state memory of the device.
In a battery operated infusion pump it may be appreciated that the state of charge of the battery is critical to ensure the continued operation of the device. In a hospital environment a nurse would have to remember to periodically recharge or change the battery in the device, making continued operation of the device absolutely dependent on changing the battery. Since a dead battery would result in the interruption of medication supplied to the patient, most infusion pumps have included some type of alarm to indicate when the battery must be changed. Since safety and reliability of medication infusion pumps are of primary importance, it is essential to have adequate safeguards in the design and operation of the device, and to avoid failure, even for relatively short periods of time.
An additional requirement has been imposed by the important design consideration of disposability. Since the portion of the device through which medication is pumped must be sterile, in most applications of infusion equipment some portions of the equipment are used only once and then disposed of, typically at regular intervals such as once daily. It is therefore desirable that the fluid pump portion of the infusion pump device be disposable, with the fluid pump being designed as an attachable cassette which is of inexpensive design, and which is easily installable onto the main pump unit. Any change in pump design must take this disposable nature of the pump portion into account.
It is desirable that the present invention ensure that the battery used to provide the primary power source for the infusion system be replaced at regular intervals, specifically at the same time the disposable pump cassette is replaced. Ensuring the simultaneous replacement of the pump cassette and the battery is therefore the primary objective of the present invention. The present invention must also retain the antiseptic nature of the disposable pump cassette while providing for the use of a fresh battery each time a new pump cassette is installed.
An incident advantage obtained in tying the replacement of the pump cassette to the replacement of the battery is that the disposal of the pump cassette will therefore be mandated with the installation of a replacement battery, thereby obviating the possibility of a disposable pump cassette being used beyond the period for which it was designed. The maximum period of use for the pump cassette will therefore be the period defined by the life of the battery. The installation of the pump cassette should therefore in the preferred embodiment involve the use of interlock means to prevent the pump cassette from being reused following its removal from the body of the infusion system after a single use of the cassette.
It is also desirable to retain a simple design to minimize the cost of construction of the disposable cassette, and to accomplish all these objects in a manner which will retain all of the advantages of reliability, durability, and safety of operation. All the advantages of the present invention will result in a superior medication infusion system having a number of advantages making the system a highly desirable alternative to systems presently available.